1. Field of the Invention
The present invention relates in general to the field of making laminated components. More particularly, the present invention relates to a method of making laminated optical components through the use of a master and several submasters. Specifically, a preferred embodiment of the present invention relates to a method of making an optical diffuser using a master and several submasters whereby the master is preserved in the process.
2. Discussion of the Related Art
Methods for manufacturing and replicating optical components utilizing a master and several submasters to achieve a final product having desired characteristics are well known. One example of such a method is that used to make viewing screens and homogenizers by generating a surface structure in a photosensitive medium using coherent light, processing the medium, and replicating the surface structure in epoxy. Several submasters, made in sequence from each other, are required to produce an optical product having the desired optical characteristics due to shrinkage of the photosensitive material at different stages in processing. For instance, to make a viewing screen having a viewing angle of, say, 30.degree. in the vertical direction by 90.degree. in the horizontal direction, a master must be made having a viewing angle of roughly 60.degree. in the vertical direction by 130.degree. in the horizontal direction. Then, a number of submasters are made in sequence from each other, each of which has a viewing angle somewhat less than the viewing angle of the master, until a submaster having close to the desired viewing angle of 30.degree. vertical by 90.degree. horizontal is achieved. The final product is then made from this last submaster.
Unfortunately, the creation of the first generation submaster from the master destroys the master and therefore that master is not available for later use should one of the subsequent submasters become unusable. It would be advantageous and highly cost effective to be able to preserve the master and store it in a library of masters to be utilized at any future time when optical products having those desired characteristics are needed.
Additionally, another problem inherent in the above-described process is that the "aspect ratio" of the surface structure of each of the submasters degenerates from generation to generation (i.e., submaster to subsequent submaster). For example, as the number of generations increase, the depth of the surface structures decreases thus reducing aspect ratio and the optical performance of the product.
Finally, optical products having light outputs with larger angular spectrums must be recorded with small feature sizes. As the feature size used for recording decreases, defects in the masters and submasters become more apparent. This problem is exacerbated for optical products having larger surface areas. Hence, the manufacturing process includes significant wasted materials if the number of defects is high.
U.S. Pat. No. 5,365,354 entitled "Grin Type Diffuser Based on Volume Holographic Material," U.S. Pat. No. 5,534,386 entitled "Homogenizer Formed Using Coherent Light and a Holographic Diffuser," and U.S. Pat. No. 5,609,939 entitled "Viewing Screen Formed Using Coherent Light," all owned by the present assignee, relate to methods for recording optical products such as diffusers and replicating those diffusers so that they may be mass produced. Each of these U.S. patents is incorporated by reference herein for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art. Related U.S. patent applications include Ser. No. 08/595,307, now U.S. Pat. No. 5,956,106, entitled "LCD With Light Source Destructuring and Shaping Device," Ser. No. 08/601,133, now U.S. Pat. No. 5,838,403, entitled "Liquid Crystal Display System with Collimated Backlighting and Non-Lambertian Diffusing," Ser. No. 08/618,539, now U.S. Pat. No. 5,735,938, entitled "Method of Making Liquid Crystal Display System," and Ser. No. 08/800,872, now U.S. Pat. No. 5,922,238, entitled "Method of Making Replicas and Compositions for Use Therewith." All the above applications are owned by the present assignee and are hereby incorporated by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.